While the college's geographic size has changed little since 1596, an additional range was added to the original E-shaped buildings in the early 17th century and the appearance of the whole college was changed significantly in the 1820s and 1830s, under the leadership of the Master at the time, William Chafy. By the early 19th century, the buildings' original red brick was unfashionable and the hall range was suffering serious structural problems.

The opening up of coal mines on estates left to the College in the 18th century provided extra funds which were to be devoted to providing a new mathematical library and accommodation for Mathematical Exhibitioners. As a result, the exterior brick was covered with a layer of cement, the existing buildings were heightened slightly, and the architectural effect was also heightened, under the supervision of Sir Jeffry Wyatville.[4]

Sidney Sussex College (1690)

In the late nineteenth century, the college's finances received a further boost from the development of the resort of Cleethorpes on College land on the Lincolnshire coast that was purchased in 1616, following a bequest for the benefit of scholars and fellows by Peter Blundell, a merchant from Tiverton, Devon.[5][6] A new wing added in 1891, to the designs of John Loughborough Pearson, is stylistically richer than the original buildings and has stone staircases whereas the stairs in the older buildings are made of timber.[7]

In the early twentieth century, a High Church group among the Fellows were instrumental in the rebuilding and enlargement of the chapel, which was provided with a richly carved interior in late seventeenth-century style, designed by T. H. Lyon, and somewhat at odds with the college's original Puritan ethos.[8]

At the beginning of the twentieth century, E.H. Griffiths wrote a ten verse song dedicated to Sidney Sussex. Each verse systematically identifies, then dismisses other Cambridge colleges for their faults, before settling on Sidney as the best college of all. The chorus exhorts the audience:

The college's adopted mascot, shown here topping an archway, is a blue and gold porcupine; from the Sidney family crest.[10]

Sidney Sussex is recognised as one of the smaller, more classical Cambridge colleges. Its current student body consists of roughly 350 undergraduate students and 190 graduates.

Academically, Sidney Sussex has tended towards a mid-table position in the unofficial Tompkins Table (placing 17th out of 29 in 2018). However, the college has traditionally excelled in certain subjects, notably Mathematics, History, Engineering and Law. It is also known for the high standard of pastoral support from the Tutorial team, and a sense of mutual support from students doing the same subject.

The college ranks fourth highest amongst Cambridge colleges in Nobel Prizes won by alumni.[11]

In the television show University Challenge, Sidney Sussex had a winning team in both 1971 and 1978–79. The 1978 team, comprising John Gilmore, John Adams, David Lidington, and Nick Graham, went on to win the "Champion of Champions" University Challenge reunion competition in 2002. The college last appeared on the television show in 2018.

It is known for producing a well-regarded May Ball for a smaller college. Notably, students created an artificial lake and canal in 2010, when the ball had a Venetian theme, to enable punting at the landlocked college.[13][14] Recent themes have included 'Light' (2014) and 'Beyond' (2016).

As with many of the smaller colleges, Sidney Sussex does not run a May Ball every year, instead running a biennial May Ball, on even numbered years. On odd numbered years, the college previously hosted an Arts Festival, which welcomed anyone in Cambridge, town or gown, to attend. Notable guest speakers at the Sidney Arts Festival include Stephen Fry, in 2015.[15] However, for 2017 it was decided instead to hold a June Event. June Events are similar to a May Ball, but are smaller, usually with a lower ticket price, and shorter running time.[16]

The Confraternitas Historica, or Confraternitas Historica Dominae Franciscae Comitis Sussexiae, is the history society of Sidney Sussex College and is reputed to be the longest-running student history society in Europe, having existed since 1910. In fact, no meetings were held from 1914 to 1919 but since, during the First World War, "the University itself almost ceased to function ... the hiatus of 1914-19 is not counted as a break in the continuity of the society".

A view of the college from Sidney Street

The Latin name of the society reflects the tastes of Jack Reynolds, the High Church Fellow who presided over its creation, who also "endowed the Society with an elaborate Latin initiation ceremony".[17] Similarly, rather than being led by a President, the student in charge of the society is instead 'Princeps'. Other society roles include the 'Magister,' 'Tribune,' 'Pontifex Maximus,' and 'Comes'. Further, during society meetings all attendees are referred to in an egalitarian, though still Latinate, manner. Regardless of academic standing or title, all attendees are given the title of 'soror' (sister) or 'frater' (brother).

Founded in 1837, the club has spent most of its time in the 2nd division of the Lent and May Bumps, with brief times spent in the 1st division. Being a small college, the club has never had the consistency to rise to take a headship of either event, and has been as high as 6th in the Lent Bumps in 1913, and 11th in the May Bumps in 1923.

A women's crew first appeared in 1978 and has spent most of its time in the lower half of the 1st division in both the Lent and May Bumps, but recently has fallen to the middle of the 2nd division of both the Lent Bumps and the May Bumps.

Former members of the college include the political and military leader Oliver Cromwell, who was among the first students - although he never graduated, dropping out after his father became ill - and his skull is now buried beneath the college's ante-chapel. His ghost was reported on a number of occasions in the 1960 after the skull's interment.[18]

Another famous alumnus was the theologian and moral philosopher William Wollaston who wrote 'Religion of Nature Delineated' (1724). Notable legal alumni include Antônio Augusto Cançado Trindade (judge on the International Court of Justice 2009 -).

Author Dorothy L. Sayers suggested that, given details in two of the stories, the fictional character Sherlock Holmes must have been at Cambridge rather than Oxford and that "of all the Cambridge colleges, Sidney Sussex (College) perhaps offered the greatest number of advantages to a man in Holmes's position and, in default of more exact information, we may tentatively place him there".[25]